Hatfield L, Hearing P
Department of Microbiology, State University of New York, Stony Brook 11794-7621.
J Virol. 1993 Jul;67(7):3931-9. doi: 10.1128/JVI.67.7.3931-3939.1993.
The inverted terminal repeat (ITR) of adenovirus type 5 (Ad5) is 103 bp in length and contains the origin of DNA replication. Cellular transcription factors NFI/CTF and NFIII/OCT-1 bind to sites within the ITR and participate in the initiation of viral DNA replication in vitro. The ITR also contains multiple copies of two conserved sequence motifs that bind the cellular transcription factors SP1 and ATF. We have analyzed a series of viruses that carry deletions at the left terminus of Ad5. A virus carrying a deletion of the NFIII/OCT-1, SP1, and ATF sites within the ITR (mutant dl309-44/107) was wild type for virus growth. However, the deletion of these elements in addition to sequences immediately flanking the ITR (mutant dl309-44/195) resulted in a virus that grew poorly. The analysis of growth parameters of these and other mutants demonstrate that the NFIII/OCT-1 and adjacent SP1 sites augment the accumulation of viral DNA following infection. The function of these elements was most evident in coinfections with a wild-type virus, suggesting that these sites enhance the ability of a limiting trans-acting factor(s), that stimulates viral DNA replication, to interact with the ITR. The results of these analyses indicate functional redundancy between different transcription elements at the left terminus of the Ad5 genome and demonstrate that the NFIII/OCT-1 site and adjacent SP1 site, previously thought to be nonessential for adenovirus growth, play a role in viral DNA replication in vivo.
5型腺病毒（Ad5）的反向末端重复序列（ITR）长度为103 bp，包含DNA复制起点。细胞转录因子NFI/CTF和NFIII/OCT-1结合到ITR内的位点，并参与体外病毒DNA复制的起始。ITR还包含与细胞转录因子SP1和ATF结合的两个保守序列基序的多个拷贝。我们分析了一系列在Ad5左端携带缺失的病毒。一种在ITR内携带NFIII/OCT-1、SP1和ATF位点缺失的病毒（突变体dl309-44/107）在病毒生长方面表现为野生型。然而，除了ITR紧邻序列外这些元件的缺失（突变体dl309-44/195）导致一种生长不良的病毒。对这些及其他突变体生长参数的分析表明，NFIII/OCT-1和相邻的SP1位点在感染后增加病毒DNA的积累。这些元件的功能在与野生型病毒共感染时最为明显，表明这些位点增强了一种限制反式作用因子与ITR相互作用的能力，该因子刺激病毒DNA复制。这些分析结果表明Ad5基因组左端不同转录元件之间存在功能冗余，并证明以前认为对腺病毒生长非必需的NFIII/OCT-1位点和相邻的SP1位点在体内病毒DNA复制中起作用。
